Spray nozzle device, in particular for spraying a cast strand

ABSTRACT

The invention relates to a spray nozzle device for spraying a cast strand or similar metallurgical products with a misty air/water mixture in the form of a mist for uniformly cooling the cast strand. The air/water mixture is produced in a mixing chamber ( 2 ) of the spraying device. Said mixing chamber acts as a diffusor and is provided with an air inlet ( 3 ), a water inlet ( 4 ), and a nozzle outlet ( 5 ) oriented approximately in alignment with the air inlet. The air inlet ( 3 ) is arranged in an air inlet nozzle ( 6 ), the tip ( 7 ) of which protrudes into the upper region of the mixing chamber and preferably has a plurality of air outlet holes ( 9 ) there, which air outlet holes are oriented perpendicular to the longitudinal axis of the mixing chamber; Water enters near the tip ( 7 ) through at least one water outlet hole ( 11 ), which is oriented perpendicular to the longitudinal axis and which is placed in such a way that the water jet exiting the water outlet hole flows past the air outlet holes ( 9 ). The spray nozzle according to the invention is characterized in that the air flow or the air pressure and the water flow or the water pressure do not influence each other.

The invention relates to a spray nozzle device, in particular for spraying a cast strand, with a mixing body that has a mixing chamber acting like a diffusor and which is provided with an air inlet, a water inlet and a nozzle outlet disposed on the side lying opposite the air inlet and through which an air/water mixture passes out.

As is well known, spray nozzles of this type are used to cool a cast strand during casting. One strives here for the most even cooling effect possible in order to prevent cracks from being able to occur in the hot cast strand during the cooling process. Hence the efforts to design the spray nozzle such that the cooling jet delivered is structurally homogeneous. However, the respectively required cooling effect is different from case to case, both for technical reasons and due to the dimensions and/or the geometry of the format to be cast. For this reason the conditions of use of the spray nozzle are variable with regard to the air and/or water pressure and the air and/or water flow.

It is a disadvantage of the previously known spray nozzles of this type that in the latter both sizes influence one another during operation. This leads to uneven subjection of the cast strand to water drop accumulations that form here and there and which have an adverse effect locally upon the cooling effect of the jet of spray to an inadmissible extent.

A spray nozzle arrangement of this type is disclosed by EP-0 161 307. This consists of a pre-atomizing head and a nozzle mouth piece with its own mixing chamber that is provided with a delivery opening for narrow fan-shaped spray patterns. The sense and purpose of the arrangement is to generate with such spray patterns a spray jet that has a high degree of atomization and that contains liquid droplets of uniform size over the entire length and width. The problems deriving from the influence of the air and water pressure or the air and water flow upon one another are not resolved satisfactorily.

The object underlying the invention is to devise a spray nozzle of the type specified at the start that guarantees a high degree of atomisation and high consistency of the spray jet independently of the casting process or the format of the product to be cooled. Furthermore, this should also be guaranteed independently of the media pressures set.

According to the invention this object is achieved in that the air inlet has a region protruding into the mixing chamber and is provided here with at least one air outlet hole orientated approximately transversely to the longitudinal axis of the mixing chamber, while the water inlet takes place through at least one hole orientated approximately transversely to the longitudinal axis close to the tip of the air inlet.

As corresponding tests have shown, it is an advantage of this arrangement that within the latter the air flow or the air pressure and the water flow or the water pressure do not influence one another to an appreciable degree, and so with changes to these sizes for procedural reasons or reasons related to format, the cooling jet delivered by the spray nozzle remains stable as regards the degree of atomization and the consistency of the cooling jet.

The invention makes provision such that the air inlet of the mixing body is formed by an aperture protruding into the mixing chamber and which is provided with at least one radial outlet hole arranged distributed around the circumference in a plane transverse to its longitudinal axis. In this way production, assembly and maintenance of the spray nozzle is simplified.

It is advantageous here if the region of the air inlet nozzle protruding into the mixing chamber has an outside diameter of less than half the inside diameter of the mixing chamber.

It is advantageous for the mode of operation of the mixing body that is striven for if the radial outlet holes are at an angle of 90°+/−max. 15° transversely to the longitudinal axis of the mixing chamber.

The air inlet nozzle can also additionally be provided with an air outlet hole orientated in the axial direction of the mixing chamber.

It is also advantageous for the mode of operation of the spray nozzle if its mixing chamber is cylindrical in form and has a length preferably twice that of the inside diameter.

The invention also makes provision such that the mixing body has a replaceable nozzle head with an outlet opening for the air/water mixture the geometry of which can be determined according to the respectively required spray pattern. In this way the nozzle can easily be adapted to variable conditions of use.

The invention and other advantages of the latter are described in more detail below by means of an exemplary embodiment with reference to the drawings. These show as follows:

FIG. 1 shows a mixing body according to the invention of a spray nozzle device, shown in section and diagrammatically,

FIG. 2 shows the spray nozzle device according to FIG. 1, in a view shown in the direction of arrow II,

FIG. 3 is a perspective view of the spray nozzle device according to FIG. 1 without a nozzle head,

FIG. 4 is a side view of the spray nozzle according to FIG. 1 without a nozzle head; and

FIG. 5 is a water pressure/water flow diagram for the spray nozzle according to FIG. 1 with two different values for air pressure.

The spray nozzle device according to FIG. 1 to FIG. 4 services to spray a cast strand with an air/water mixture in order to cool it during casting. The mixing body 1 has a mixing chamber 2 that is provided with an air inlet 3, a water inlet 4 and a nozzle outlet 5.

The mixing chamber 2 of the mixing body 1 is cylindrical in form. Its length is approx. twice the inside diameter of the mixing chamber. The air inlet 3 is disposed in an air inlet nozzle 6 the tip 7 of which protrudes into the upper region of the mixing chamber. The air inlet nozzle 6 is orientated coaxially to the mixing chamber 2, and its outside diameter is smaller here than half the inside diameter of the mixing chamber. In this region it is provided with air outlet holes 9 passing radially out of the mixing chamber approximately transversely to the longitudinal axis of the mixing chamber and which are distributed evenly around the circumference in a plane transverse to the longitudinal axis.

The water inlet 4 discharges into the mixing chamber 2 close to the tip 7 of the air inlet 3 with a water outlet hole 11 orientated transversely to its longitudinal axis and the distance of which from the tip 7 is such that the water jet flowing out of it does not affect the air outlet holes 9. The spray nozzle described is equipped with just one water outlet hole. However, it can in principle also be provided with a number of water outlet holes arranged distributed around the circumference.

The water inlet 4 is formed by a hole 11′ running approximately parallel to the longitudinal axis of the mixing body 1 and by this transverse water outlet hole 11. Contained within the hole 11′ is initially a replaceable filter 19 and then an aperture 4′, and it is additionally provided with an over-hole 11′ which is formed as an extension passing from the transverse water outlet hole 11 and serves to calm the water conveyed into the water outlet hole 11.

Furthermore, the radial air outlet holes 9 are made at a slight angle to the perpendicular plane, the angle of inclination being able to vary within a range of +/−max. 15°. Moreover, they could also be orientated at least approximately tangentially instead of radially, by means of which swirl of the water jet flowing into the mixing chamber is generated which is associated with evenly finely structured atomisation of the air/water mixture.

The cylindrically formed mixing body 1 has in an extension of the mixing chamber 2 an appendage 14, which is also cylindrical, to the end of which is attached a replaceable nozzle head 15 with an air/water mixture outlet opening 16. The connection of the nozzle head 15 to the mixing body 1 is disposed in the appendage 14 of the mixing body.

A bayonet closure or a similarly releaseable connection could also be used instead of this type of correctly functioning screw connection. Due to the replaceability of the nozzle head 15 the spray pattern of the nozzle can easily be adapted to the respective conditions of use from case to case depending on the form of the one or the number of outlet openings.

Furthermore, according to FIG. 3 and FIG. 4 centring means 17 for positioning of the nozzle head 15 with respect to the mixing body 1 are indicated on the lower face side of the cylindrical appendage 14.

An aperture 4′ is respectively provided in the air inlet 3 and the water inlet 4 for throttling the delivered air or the water.

Needless to say, the advantages of the spray nozzle according to the invention also apply when another comparable type of gas/liquid mixture is used as coolant instead of the air/water mixture.

Both the air outlet holes and the water outlet holes can be orientated at least approximately tangentially instead of radially.

An extension pipe could also be provided between the mixing body 1 and the nozzle outlet 5 if, for example, smaller strand formats are cast.

If operation is interrupted or if casting is halted, air alone may be delivered through the spray nozzle device in order to guarantee sufficient cooling of the latter.

In order to determine the spray output of the nozzle, tests are carried out with variable pressure and flow values. As can be seen from the diagram according to FIG. 5 it emerges from the test results that the two sizes do not influence one another in the spray nozzle according to the invention. The water pressure (bar) is plotted on the x axis and the water and air flow (1/min and m³/h) on the x axis in the diagram. Lines 12 a, 12 b and 13 show the air flow sequence 1A-2A and the water flow sequence 1B-2B with a constant air pressure of 2 bar or 3 bar and a constant air flow of 6.0 m³/h or 7.8 m³/h.

The following pressure and flow values were determined by the tests:

Example Air pressure Water pressure Air flow Water flow 1 2 bar 0.5 bar 1A-2A: 6.0 m³/h 1B: 0.81/min 2 2 bar 8.0 bar 1A-2A: 6.0 m³/h 2B: 3.41/min 3 bar 0.5 bar 7.8 m³/h 1B: 0.81/min 3 bar 8.0 bar 7.8 m³/h 2B: 3.41/min

It can be gathered from the table that the course of the water flow curve 1B-2B remains constant when the air pressure increases from 2 to 3 bar or when the air flow is increased from 6.0 to 7.8 m³/h. The spray nozzle according to the invention thus guarantees a consistently homogeneous character of the air/water mixture, independently of the respectively required cooling effect. There is therefore mutual independency over a large pressure range of the air and water pressure. 

1. A spray nozzle device, in particular for spraying a cast strand, with a mixing body that has a mixing chamber (2) acting like a diffusor and which is provided with an air inlet (3), a water inlet (4) and a nozzle outlet (5) disposed on the side lying opposite the air inlet (3) and through which an air/water mixture passes out, characterised in that the air inlet (3) has a region protruding into the mixing chamber (2) and is provided there with at least one air outlet hole (9) orientated approximately transversely to the longitudinal axis of the mixing chamber, while the water inlet (4) takes place through at least one hole (11) orientated approximately transversely to the longitudinal axis close to the tip (7) of the air inlet (3).
 2. The spray nozzle device according to claim 1, characterised in that the air inlet (3) is formed by an air inlet nozzle (6) protruding into the mixing chamber (2) and which is provided with the at least one air outlet hole (9) arranged distributed around the circumference in a plane transverse to the longitudinal axis.
 3. The spray nozzle device according to claim 2, characterised in that the region of the air inlet nozzle (6) protruding into the mixing chamber (2) has an outside diameter of less than half the inside diameter of the mixing chamber (2).
 4. The spray nozzle device according to claim 2, characterised in that the mixing chamber (2) is cylindrical in form and has a length approximately twice that of its inside diameter.
 5. The spray nozzle device according to claim 2, characterised in that the air outlet holes (9) are at an angle of 90°+/−max. 15° transversely to the longitudinal axis of the mixing chamber (2), the at least one water outlet hole (11) being positioned such that the water jet passing out of it flows past the air outlet holes (9).
 6. The spray nozzle device according to claim 2, characterised in that the air outlet holes (9) are angled in a fan shape in the plane transverse to the longitudinal axis of the mixing chamber (2).
 7. The spray nozzle device according to claim 2, characterised in that the air inlet nozzle (6) is additionally provided with an air outlet hole (8) orientated in the axial direction of the mixing chamber (2).
 8. The spray nozzle device according to claim 1, characterised in that the nozzle outlet (5) has a replaceable nozzle head (15) with an outlet opening (16) for the air/water mixture the geometry of which can be determined according to the respectively required spray pattern.
 9. The spray nozzle device according to claim 1, characterised in that an extension pipe is provided between the mixing body (1) and the nozzle outlet (5).
 10. The spray nozzle device according to claim 1, characterised in that an aperture (4′) is respectively provided in the water inlet (4) and the air inlet (3) for throttling the delivered water or the air.
 11. The spray nozzle device according to claim 1, characterised in that the water inlet (4) is formed by a hole (11′) running approximately parallel to the longitudinal axis of the mixing body (1) and by this transverse water outlet hole (11), an aperture (4′) being contained in the hole (11′).
 12. The spray nozzle device according to claim 11, characterised in that the hole (11′) is provided with an over-hole (11″) provided as an extension passing out of the transverse water outlet hole (11) and which serves to calm the water conveyed into the water outlet hole (11). 